Multilith models and other makes of offset printing machines, two color printing heads, etc., have water fountain trays with a water fountain roller positioned therein. The water or water fountain solution is transferred from the water fountain roller to a plate cylinder that carries the printing plate that in turn contacts a blanket cylinder that transfers the image to the paper passing therethrough. When operating such printing machines and the like, it sometimes occurs that a disproportionate amount of water builds up on sections of the water fountain roller. This can occur where, for example, narrow paper stock, envelopes or the like are run through the printing machine. When running narrow stocks, the area adjacent to the paper stock will often accumulate an excessive amount of water or fountain solution in a very short length of running time, because there is no water absorption by the paper stock taking place in this area. This results in an immediate imbalance of ink and fountain solution and excessive moisture build up in this area. While the plate must be wet enough to prevent blacking-up (dry plates), the water should not be so excessive as to create a water imbalance with the ink, or of a sufficient excess magnitude as to feed back into the ink unit itself. Thus, it is desirable to control the amount of water on the fountain roller.
Also where a portion of the roller may be running dry, the amount of water can be increased on the roller thus providing additional water or fountain fluid to the dry portion of the roller. The resultant excess fluid on the other areas of the water fountain roller is then controlled by the wiper unit.
There have been attempts in the past to use devices to contol the amount of water on the water fountain roller. These devices generally comprise a pivot bar mounted above the water fountain roller with wipers connected thereto. These wipers have end tips that ride on the surface of the fountain roller, or in reality on a film of water, without wiping any water off the fountain roller. The pivot bars that support the wipers are expensive to install, are a mechanical problem, are fixed in position, and do not provide an adequate control of excess fountain fluid on the roller.
So it is desirable to have a new and improved water fountain control wiper unit that provides complete control of the water on the fountan roller and relieves the operator of the various and troublesome water problems encountered in such units, and that may be selectively adjusted by the operator to compensate for different water distributions at selected areas across the surface of the water fountain roller, permitting easier operation of the machine and improved printing results.